My families dogs are so used to getting treats and surprises that they ran into a rut with fun new treats to try. We got them each a kong and began putting peanut butter in it and they loved it! It probably got a little unhealthy for them though, and we occasionally switched it out for spray cheese, the type you buy for humans and put on crackers and such. While we were walking through the pet store a few weeks ago, I noticed that they actually made a specific spray cheese for the kong toys designed for dogs! I was sure it'd be much healthier for them too, as it was designed just for dogs. We use it when we know we'll be gone for a longer portion of the day so that they have something to do while trying to get the cheese out of the Kong. They also run right to us when they hear the cheese going into the kong. It does smell a little strange, but that was to be expected I think. They eat it right up, and the best part is it doesn't need to go take up room in the refrigerator. All around a great treat!